Ben Barden's answer has already covered the healing from Circle of the Moon druids specifically, so I'll expand on healing for that party composition in general.
I'm currently playing a campaign with an almost-identical party (Sorcerer instead of Warlock); Our Druid (Circle of Twilight) usually avoids healing spells except in the most dire of situations, due to the character's personality. However, as long as they position intelligently, this isn't an issue for the rest of the party - Both of the frontline classes, Paladin and Fighter, have healing abilities, with the Paladin's Lay on Hands being particularly important for burst healing. Meanwhile, the Ranger's Healing Spirit is crucial for drawn-out fights, though even more location-dependant - While many DMs will limit its out-of-combat usage (10d6/character is, frankly, broken), in-combat it can be used both to counteract damage and spot-heal downed players. Add Cure Wounds, potions of healing, and short rests, and you should have no trouble with sustainability.
The most important thing for this party is going to be positioning - The primary source of burst healing, the Paladin, can only heal at Touch range, which means if your Rogue gets caught while scouting ahead or your spellcasters flanked, you are going to have serious trouble, especially as Healing Spirit (which can only be moved 30 feet/round) should usually be adjacent to the most dangerous enemy (to allow your melee fighters to rotate through it without provoking attacks of opportunity).